The goal of this proposal is to investigate the auditory processing of natural sounds. This problem will be investigated in the auditory forebrain of awake, behaving songbirds. The statistical structure of natural sounds will be analysed using a variety of quantitative techniques, and synthetic sounds that preserve or alter specific aspects of natural sounds will be generated. Electrophysiological recordings in a chronic preparation will be obtained, using mufti-electrode arrays, from a population of neurons in successive stages of the auditory pathway. New theoretical methods for the analysis of the neural coding of natural sounds will be applied to quantitatively describe the features of sounds to which auditory forebrain neurons are sensitive and information theory will be applied to quantify the amount of information conveyed by the neural responses. Processing capabilities of the auditory circuits that are innate as well as those that depend on learning and development will be investigated by comparing the neural responses in the juvenile and the adult auditory systems. Such circuitry is analogous in a variety of ways to the innate neural networks that must exist in human infants and endow them with innate responsiveness to speech sounds of all human languages at birth. Thus, the results of this investigation will be relevant to disorders involving deficits in speech acquisition and learning.